# calculation of studentized deleted residuals

I have a problem that asks me to calculate studentized deleted residuals from the following set of residuals:

From the original dataset:

The Hat matrix, diagonal elements hii, SSE/MSE, formula for studentized residuals, and final calculation of the residuals are below:

s

However, I cannot reproduce these results given the formula! For example, taking the square root of a negative residual in the numerator results in an imaginary number if x>0. Is there another way to calculate these residuals, or something I am I just not getting it? Thanks!

$$\frac{e_i}{\sqrt{SSE(1-h_{ii})-e_i^2}}$$
$$sign(e_i)\left[ \frac{e_i^2}{SSE(1-h_{ii})-e_i^2} \right]^{1/2}$$